1. Field of the Invention
The instant invention relates to a detection monitoring system and in particular relates to monitoring deflections in a roof structure.
2. Description of the Prior Art
As a rigid structure is exposed to external stresses, the supporting structure will often begin to deform and display deflections before the structure actually fails and collapses. For example, as weight accumulates on a roof, it begins to overload the roof's supporting structure, causing deflections in the roof's structure. The stress of the weight may eventually overload the roof's structure, thereby causing the roof to collapse. There exists a need to monitor and detect these deflections to determine when a support structure such as a roof is in danger of collapse.
Some prior control systems measured the deformation resulting from earthquakes and other external forces. Some of these systems would respond to the deformation by applying countervailing forces to compensate for them. U.S. Pat. No. 4,964,264 issued to Takuji Korbori et al. on Oct. 23, 1990 describes a rigidity control system in which the tension of the control elements are adjusted to attenuate deformation in a building structure resulting from the vibrational forces of, e.g., an earthquake. U.S. Pat. No. 4,956,947 issued to Leonard E. Middleton on Sep. 18, 1990 describes a tendon system for inhibiting sway in a building. The tendon system is responsive to changes in the deflection of the building as measured by a steady beam focused on a sensor target on the building structure. U.S. Pat. No. 4,429,496 issued to Sami F. Masri on Feb. 7, 1984 describes a method and apparatus for the active control and dampening of flexible structures in response to vibrational shocks from earthquakes and other such events. A corrective force is applied to the structure in pulses to dissipate the vibrational energy from the earthquake and to disorganize the resulting harmonic motion of the structure.
Some prior control systems detect and monitor the deformation of a building structure, and trigger an alarm upon such detection. U.S. Pat. No. 4,889,997 issued to Andrea Tomiolo on Dec. 26, 1989 describes a process and device for measuring the displacement of building structures using laser beams. A rotating prism directs the laser beam towards various sensor targets, and any deviation from the last reading activates an alarm. U.S. Pat. No. 4,843,372 issued to Thomas Savino on Jun. 27, 1989 describes a bridge sway and deflection system using a laser and mirror system. A laser beam is generated at one side of a bridge and passed through a series of apertures placed along the supporting vertical columns of the bridge. If any deflection occurs along the bridge's support columns, the aperture will move out of alignment with the laser beam and signal a general structural fault in the bridge. Savino's system detects general faults in the bridge structure, but cannot localize the fault occurrence. Because movement of any one of the apertures could break the circuit created by the laser beam, Savino is not capable of detecting the fault' s location.
Other systems are known in which a laser is used to detect objects which pass a certain threshold position. U.S. Pat. No. 3,711,846 issued to Gabor Schlisser et al. on Jan. 16, 1973 describes an alarm system wherein a laser beam is directed and repeated along the perimeter of an enclosed area. U.S. Pat. No. 3,335,285 issued to John Gally, Jr. et al. on Aug. 8, 1967 describes a photoelectric system for detecting objects using a laser light source.
Other detection and monitoring systems have used a variety of other types of sensors. U.S. Pat. No. 4,936,060 issued to Richard Gelinas et al. on Jun. 26, 1990 describes a flexible roof control system using a plurality of radar units to measure the height of the roof. Published European Patent Application No. 0 377 880 A1 for Giovanni Azzimonti and published on Jul. 18, 1990 describes a structural facade wherein each panel of the facade includes at least one sensor for signalling possible shifts of the panel.
None of the above patent references, either alone or in combination, is seen to describe the instant invention as claimed. While these and other patents disclose the use of lasers to measure misalignments and detect intrusions, the known prior art does not disclose or suggest the deflection monitoring system of the instant invention.